1. Field of the Invention
The present invention relates to a flame retardant synthetic fiber and a flame retardant fiber composite having high flame retardance, which can be employed preferably for textile products requiring high flame retardance used in bedding, furniture, etc. due to the expression of very high carbonization, shape holding property, and self-extinguishing property during burning, a production method therefor, and a textile product.
2. Related Background Art
Recently, there is an increasing demand for ensuring the safety of food, clothing and shelter, and the necessity for flame retardant materials is increasing from the viewpoint of flame proofing. Under such circumstances, particularly, in order to prevent fire during sleeping, which causes serious human damage when it occurs, the necessity for providing flame retardance to materials to be used in bedding, furniture, etc. is increasing.
In upholstered products such as bedding and furniture, inflammable materials such as cotton, polyester, and urethane foam are used frequently inside of and on the surfaces of the upholstered products for the purpose of comfort during use and design. For ensuring the flame retardance thereof, it is important to use appropriate flame retardant materials in these products to provide high flame retardance for preventing inflammation of the inflammable materials for a long period of time. Further, the flame retardant materials also need to maintain the comfort and design of the products such as bedding and furniture.
As a flame retardant fiber material that is a flame retardant material using fibers, various flame retardant fibers and flame proofing agents have been considered in the past. However, flame retardant fiber materials have not been found that sufficiently satisfy the following requirements: high flame retardance, and comfort and design required of the products such as bedding and furniture.
For example, regarding cotton, there is a procedure such as a so-called post-processed flame proofing in which the cotton is coated with a flame proofing agent. However, the post-processed flame proofing has problems related to the uniformity of the adhesion of a flame proofing agent, the hardening of cloth caused by the adhesion of a flame proofing agent, the elimination of a flame proofing agent caused by washing, the safety, and the like.
Further, polyester-based fibers that are an inexpensive material are melted during burning. Therefore, when fabric is formed of only polyester-based fibers, the fabric will have a hole during burning, which makes it difficult to maintain a configuration, and the above-mentioned cotton or urethane foam used in bedding or furniture is ignited. Thus, the polyester-based fibers have insufficient performance. There also are flame retardant polyester fibers containing phosphorus atoms and the like; however, the behavior of the flame retardant polyester fibers containing phosphorus atoms and the like during burning is similar to the one described above, and hence, the flame retardant polyester fibers containing phosphorus atoms and the like are melted finally, which is insufficient performance.
With a method for obtaining high flame retardant modacrylic fibers by adding antimony trioxide, antimony pentoxide, and magnesium oxide to a spinning dope solution, although the fibers thus obtained can be provided with fire retardance, they do not satisfy a shielding property with respect to flame and heat. As fibers having these performances, i.e., providing flame retardance and satisfying a shielding property with respect to flame and heat, there are cross-linking high flame retardant acrylic fibers with a polymer containing glycidylmethacrylate added thereto (JP 2005-179876 A). However, when the cross-linking high flame retardant acrylic fibers with a polymer containing glycidylmethacrylate added thereto are exposed to strong flame such as burner flame, the fibers are decomposed so that flame passes therethrough finally.
Further, there are high flame retardant shielding modacrylic fibers with solid-phase flame retardants such as water glass and zinc oxide added thereto (JP 2006-225805A). These fibers are excellent in an extinguishing property and flame shielding performance; however, a carbonized layer to be formed during burning is hard, and the shrinkage variation of the fibers is large depending upon the kind of furniture and bedding and the shape of a burnt portion. Therefore, a stress is applied to the carbonized layer formed during burning, and cracks may be generated in the carbonized layer and a hole may be opened in the carbonized layer even under a small load. In order to solve this problem, modacrylic fibers have been proposed, in which zinc oxide and a condensed phosphate-based compound are added to control the carbonizing speed during shrinkage, whereby cracks are unlikely to be generated (JP 2007-291570 A). When these fibers are used, high flame retardance cannot be obtained unless a plurality of limited kinds of fibers are used with a further limited fiber mixed ratio.
Further, a production method for obtaining acrylic synthetic fibers with satisfactory heat resistance and shrinkage by performing a wet-heat stretched heat treatment has been proposed (JP 58 (1983)-156014 A). However, a residual shrinkage stress cannot be removed sufficiently since a heat treatment is performed in a stretched state, and the fibers shrink remarkably at a high temperature of 200° C. or higher such as that of flame although the shrinkage can be suppressed at a relatively low temperature of 160° C. As a result, the fibers to be obtained have degraded flame retardance. Further, the use with other fibers required as a practical textile product is not considered at all, so that the fibers to be obtained cannot withstand the use as a practical flame retardant material.
A flame retardant fiber mixture in which halogen-containing fibers that are made highly flame retardant by the addition of a large amount of a flame retardant are combined with non-flame retardant fibers (JP 61 (1986)-89339 A), and bulky flame retardant nonwoven fabric composed of fibers that are essentially flame retardant, halogen-containing fibers, and the like (U.S. Pat. No. 7,259,117) have been proposed respectively.
However, according to these methods, the shapes before burning such as fabric and woven fabric cannot be maintained during burning, so that desired flame retardance, in particular, a flame shielding property cannot be ensured; high flame retardance is not obtained unless a plurality of limited kinds of fibers are used with a further limited fiber mixed ratio, which causes trouble in terms of a product design and production steps. Although, generally, heat-resistant fibers and fibers that are essentially flame retardant are likely to have desired flame retardance, the fibers are hard and brittle in most cases, so that it is very difficult to handle the fibers in the course of production and processing of texture and the costs are high. Also, high flame retardance cannot be obtained without a further limited fiber mixed ratio, which causes trouble in terms of a product design and production steps.